functional programming in R

Question

I have been reading the Functionals from github. One suggestion in the page was to use call_function if one is working with a list of functions. Here is the code from the page:

call_fun <- function(f, ...) f(...)
f <- list(sum, mean, median, sd)
lapply(f, call_fun, x = runif(1e3))

The output was posted as:

# [[1]]
# [1] 498
# 
# [[2]]
# [1] 0.498
# 
# [[3]]
# [1] 0.49
# 
# [[4]]
# [1] 0.29

However, I was not able to replicate the above results. I got the error:

Error in FUN(X[[4L]], ...) : could not find function "f"

Am I missing something here?

eddi · Accepted Answer · 2013-08-15 16:47:23Z

5

You have redefined the function sd:

sd = 2

call_fun <- function(f, ...) f(...)
f <- list(sum, mean, median, sd)
lapply(f, call_fun, x = runif(1e3))
#Error in FUN(X[[4L]], ...) : could not find function "f"

Restart your session or do rm(sd).

answered Aug 15, 2013 at 16:47

eddi

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3 Comments

Metrics Over a year ago

Thanks @eddi. I am not sure whether my question will be useful for future users. I will be happy to delete if it seems trivial.

IRTFM Over a year ago

I'm not sure that you can delete it. It already has an upvote (mine) and upvotes on the answer (mine and anothers). I'm still curious if there is a programmatic way to handle the problem. I tried call_fun <- function(f, ...) match.fun(f)(...) which succeeds in the simple case and fails in the same manner with sd==5 in the environment.

eddi Over a year ago

@Metrics I've run into this exact same issue before with sd (there are only so many two letter variable names), so it's probably not too uncommon of a mistake (not so sure though one can find this question through a search engine)

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